Electric-battery depolarizer.



'- MAJOR E. HOLMES, OF LAHWOOD, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO

NATIONAL CARBON COMPANY, INC., A CORPORATION OF NEW YORK.

ELECTRIC-BATTERY DEPOLARIZEB.

To all whom it may concern.-

Be it known that I, MAJOR E. Homes, a citizen of the United States, residing at Lakewood, in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Electric-Battery Depolarizers, of which the following is a full, clear, and exact description.

My invention relates to depolarizers'which are generally required for the efiicient working of electric batteries.

The use of depolarizers in electric batteries was one of the early developments in the battery art, but comparatively few substances have been found to ss suflicient depolarizing properties to commercially successful. In fact, the oxide of manganese and copper are the only ones used to any extent in commercial primary batteries. The

object of my invention is to procure new materials that have marked advantages over present depolarizers, as will be m the appended description wit reference to the drawings in which: Figure 1 graphically izer toward nascent hydrogen.

Fig. 2 shows curves of per cent. voltage drop during service. I

Oxids in order to be suitable for depolarizers in electric cells'of the modern dry cell type, must possess certain chemical and salts which are the usual electrolytes in cells of the type referred to. They should, when mixed with graphite, have the capacity of absorbing a large volume of electrolytic solution. They should have those )roperties which would permit of their being molded with graphite into a dense mass to effect good contact between the despeomoation of Letters Patent.

Application filed January 7, me. Serial No. raves.

inted out illustrates the be-' havior of mixtures of graphite and dep0lar-- Patented July is, 1918.

polarizer and conducting material." .I have found that molybednum trioxid possesses the above properties in a very satisfactory degree.

here is still another. property which is difiicult to definitely predict from a knowledge of specific chemical and physical properties of the material, and which is of supreme importance in determining the worth of such substance as a depolarizer. I refer to the reactivity of mixtures of the depolarizer and. graphite toward nascent hydrogen. In performing this primary function of a depolarizer, I have found that molybdenum trioxid greatly exceeds the capacity of the ordinary depolarizers. With this, and-other depolarizers, I have determined, let the maximum current density at which hydrogen ions may be discharged against the surface of the mixture of the depolarizer and graphite without gas evolution,and 2nd, the length of time that the hydrogen ions can be discharged at a rate .com arable with that in ordinary service con itions, without gas evolution.

I have graphically shown in Fi 1 of the drawings the results in the first etermination where the ordinates represent current density and the abscissas mixtures of graphite and depolarizer. In this figure curve A gives the results with molybdenum trioxid and cave B that of pyrolusite. A comparison of the two curves shows at once ,the superiority of molybdenum trioxid.

In the second determination above mentioned, with a current density of twenty-one hundredths amperes per square inch cross section, molybdenum trioxid shows an advantage of about 1000% over pyrolusite. That is, hydrogen gas will commence to evolve with pyrolusite in about one tenth the mixed has considerable influence on the various factors of the dry cell, and therefore I have made tests to determine the best pro portion to be used, all things considered. Ihe following table gives the various charoxid, when mixed with graphite, using an electrolyte consisting of 100 parts water, 18 parts Zinc chlorid and 33 parts ammonium voltage o'f a cellin which a aoteristics of the depolarizer of varying V The drop in amounts of pyroluslte and molybdenum tridepolarizer is used 1s very instructive 1n re- MiX'mtio' I I Servigithrough 2% Initial Initial curms to closed cir- Lot. Depolanzer. Volts. mm wit vow Depol. Graph. .5 v. .s v.

O.pyrolusite 90 1.62 .7 32 78 min... 1 1. .....do so 20 1.59 .1:-.4 ,21mm.... 64min... 1. 70 so 1.51 1.9 42min... 1. .60 40 1.58 1.8, 21 1111111.. 40min... 1. 5.. 90. 10 1.18 .4 0-min.... 2161m'n... c 6.. so 20 1.26 .6 65min 212min;.. 7 7o 30 1.30 -1.9 55min 180min... s J10 so '40 1.25 1.5 52min 156mm... 9 None (mixconsistingwhollyofgraphite).. 1.38 .5 9sec.....- 37 sec....

gard to the worth of the depolarizer and I therefore have given in Fig. 2 curves to illustrate the per cent. drop involtage. In this figure are plotted the percentages of drop in voltage of the two depolarizers on 2% ohms continuous service test, curves B and 'A relating to pyrolusite and molybe denum trioxid respectively. That is, electric cells are made up with the depolarizers, their circuits closed through the resistance of 2% ohms," and the curve plotted from data obtained in such test.- In the figure the ordi.- nates represent the percentage drop in volt-. age, while the abscissas represent the service life in minutes; It will" be evident from an inspection of the data given in the precedingtable, that the best ratio of pyrolusite to graphite is 90 to 10, and of molybdenum,

trioxid to graphite is 80 to 20. The cell from which the percentage drop was calculated in .the two cases was therefore constructed with this ratio-of materials.

An inspection of the data in the table also 5 shows that the initial voltage of molybdenum trioxid is less than that of pyrolus1te;but since the percentage drop of voltage onrigorous service, such as in miniature'or flashvoltage lamp with crystalline powder when obtained by crystallization from themelt. Before using this material in dry'cells, such would preferably be crushed into powdered form and mixed with graphite or other form of carbon to furnish the proper conductivity. The mixture of oXid and graphite, moistened with electrolyte, would then be tamped around the carbon electrode of a dry cell, for instance inside a-zinc, or other electrode con tainer, 'with'a bibulous lining separating it from the'latter. In the so-called Leclanch sss sess type of dry cell, which is the one most generally used. :the electrolyte referred to would 'lJG'ClllOllClS of: ammonium and zinc, though other electrolytes may be used.

:I have also found that certain oXid salts and complex compounds of molybdenum have advantageous properties when used as depolarizers. For instance, molybdates of sodium and lead can be used as depolarizers.

There are many other salts of this nature capable of use, as molybdenum trioxid has a tendency to form mol-ybdates, and .poly- .75

molybdates in large number so that I propose to use molybdates having the generalformula mMO-p MoO Where 3/ is equal to or greater than m. In this formula .w and 3 represent numerical coeflicients and -M a metal.

As an illustration of a complex mol bdate, I may mention ammonium-phosp 0- molybdate (NIL) PO -12MoO This has proven to be very satisfactory as a depolarizer and is less reducible by zinc in NIL, solution than M00 Molybdenum trioxid is capable of hydration in accordance with the formula MoO -wH O, and such hydrates are within the purvey of my invention. While there would be great advantage in usin molybdenum depolarizers altogether in ry cells,

the question of'expense may make it advi's- H Having'described my invention, what I sisting of substantially 80 parts molybdic claim is trioxid and 20 parts graphite.

1. In prima batteries, a depolarizer con- In testimony whereof, I hereunto aflix my taining molyb enum trioxid. signature. 7

2. In primary batteries, ositive and negat tive electrodes and a depolarizing mix con- MAJOR E. HOLMES. 

